Crap, it doesn't work! And it's your own fault at that. Why is your company name "XYZ" in its stand-alone version but "XYC" in the web address?
Okay, on to the decidedly-not-simple-anymore solution. The web address contains periods to its left & right, and while there may be a period to the right of the actual name, there never should be one at its left.
Try this:
(?<!\.|\w)XYZ\b
Here is, by the way, another reason not to use this trick to capitalize your company name. If the company name is a common word in all caps ("WORD", for example), all occurrences of that word in lowercase will be automatically picked up as the company name.